XSTAR is a computer program for
calculating the physical conditions and emission spectra of photoionized
gases.

Current Version

Current version is 2.39, also available as part of heasoft 6.21.

How Do I Get XSTAR?

Xstar is avaible in several different ways.

The XSTAR package is now integrated and distributed with the HEASARC's
standard HEADAS package, so if your facility has this package installed then you
already have access to xstar.

A bug has been found in xstar version 2.53 which affects the spectrum output to xout_spect1.fits. This therefore also affects the atable created by xstar2xspec. A patch is available from the heasoft 'known issues' page. Or get the current develop version.

XSTAR is also available as a standalone
package. The standalone XSTAR (or the full HEADAS), is available
in either source or binary versions and it can be downloaded from
here .

The release version of xstar is now available on hera.
To use it, you must install fv and set up your environment to use it (fv is part of the standard heasoft software
distribution or it can be installed standalone), and type
'fv -r xstar'. Input parameters are specified by prompting or else on the
command line. Currently the output is buffered in large blocks, rather than
printing each line of output as processing progresses. Thus it may appear that
nothing is happening for a while until the buffer fills and is sent
to your screen. It's also possible to start up the xstar task in hera, and then retrieve the
results later, without having to keep the command window open.
One would need to specify all the parameters directly on the command line,
and also add a "-nowait " flag. For example:
"fv -r -nowait me@milkyway.gsfc.nasa.gov xstar cfrac=1. temperature=400. ..."
You will then receive an email message when the job is finished, with
instructions on how to retrieve the output.

A utility has been created for extracting atomic data and rates from the xstar database.
This utility is a standalone fortran program, which calls many of the xstar routines,
and returns the rate (forward and reverse) and raw atomic data for a single type of
rate for a single ion. It can be found
here

An analytic model for calculating warm absorber and emitter spectra within xspec
is available. This has the advantage that it avoids the intrinsic approximations
associated with use of tables for absorption with variable abundances
treated as multiplicative parameters, and the intrinsic clumsiness
of the use of tables. It also allows the use of arbitrary spectral
resolution, not limited by the internal xstar spectral resolution.
To use it, download the tarfile, unzip and untar
in your user area, and follow the installation instructions contained
in the README.
This includes the analogous routine which simulates the absorption (and emission) by a
gas in coronal equilibrium.
Scattered emission can be modeled using the 'windabs' model.
These routines are still
in the testing phase, so please send reports of bugs and problems.

The develop version of warmabs,
is here. It must be used with population files
constructed with the develop version of xstar.

A version of xstar which allows for parallel computation of a grid of models
has been developed by Michael Noble of MIT.
pvm_xstar fosters
parallel execution of XSTAR over large, time-consuming sets of
parameters.

A php tool for making the xstinitable.par file needed by xstar2xspec is provided
by D. Maitra of the University of Michigan
here.
This is a GUI form which
produces the file in ascii. No error checking is provided.

An analytic model for calculating interstellar absorption within xspec
is available. This utilizes the same atomic data as xstar and warmabs but allows the
column densities of the ions to be free parameters rather than being prescribed by
ionization equilibrium. It also allows the use of arbitrary spectral
resolution, not limited by the internal xstar spectral resolution.
To use it, download the tarfile, unzip and untar
in your user area, and follow the installation instructions contained
in the README.
A paper describing the tool in more detail is available here.

Online Documentation

XSTAR documentation is included as part of the standard source
distribution and is also viewable online
or can be downloaded as a PostScript
file or HTML.